1. Technical Field
The technical field relates to a three-dimensional image pickup apparatus for generating a three-dimensional image (stereoscopic image) by capturing an image for the left eye and an image for the right eye, and more particularly to a three-dimensional image pickup apparatus having a configuration capable of optically altering a focal length and a convergence angle.
2. Related Art
Today, a three-dimensional image pickup apparatus that generates a three-dimensional image (stereoscopic image) by capturing two images (a left-eye image and a right-eye image) comes into the spotlight. In the three-dimensional image, an image of a subject on the left-eye image and an image of the same subject on the right-eye image both have disparity corresponding to the binocular disparity of the right and left eyes of a human. When displaying the three-dimensional image, the left-eye image is presented to the left eye of a viewer and the right-eye image is presented to the right eye of the viewer, synchronously. The viewer of the three-dimensional image can use the disparity as a cue to perceive the depth of a subject, that is, stereoscopic effects.
The angle formed by an optical axis of a left-eye image camera for capturing the left-eye image and an optical axis of a right-eye image camera for capturing the right-eye image is referred to as a convergence angle. A plane which includes the intersecting point of the two optical axes forming the convergence angle and is parallel to the installation interval of the two cameras is referred to as a reference plane. In the three-dimensional image, a subject existing on the reference plane has a parallax of zero, and a subject not existing on the reference plane has a parallax of a magnitude and a direction depending on the distance and fore-and-aft relationship between the subject and the reference plane. The viewer who watches the three-dimensional image displayed on a screen plane of a three-dimensional display device perceives an object recorded in the three-dimensional image with zero parallax as if existing on the screen plane, and perceives an object recorded in the three-dimensional image with non-zero parallax as if existing farther or closer than the screen plane. In other words, a subject located farther than the reference plane at the shooting is perceived by the viewer with depth effects, and a subject located closer than the reference plane at the shooting is perceived by the viewer with projecting effects.
Accordingly, when capturing a three-dimensional image, it is extremely important to appropriately control a position of the reference plane. The position of the reference plane is determined in accordance with the convergence angle of the three-dimensional image pickup apparatus. Therefore, in an imaging of a three-dimensional image, appropriate control of the convergence angle is extremely important.
In the meantime, if a subject image having an extremely large parallax is included in a three-dimensional image, a certain discomfort may arise in the viewer. To avoid such situations, it is necessary to adjust the parallax of the subject by controlling the convergence angle of the three-dimensional image pickup apparatus to vary the position of the reference plane so as to create a three-dimensional image that may not provide the viewer with discomfort feeling.
JP 2010-103895A discloses a twin-lens image pickup apparatus for creating a three-dimensional image. This twin-lens image pickup apparatus is designed to capture a plurality of three-dimensional images automatically and continuously while controlling a built-in optical image stabilizer (lens-shift type) to vary the optical axes of the optical systems for altering the convergence angle variously. Accordingly, a user can select a three-dimensional image(s) which has stereoscopic effects suited for his/her taste from the three-dimensional images generated through the continuous shots.